Micrometer bore gauge



Dec. 14, 1948. H. R. FoRsMARK n* 2,456,497

MICROMETER BOREjGAUGE .Filed March 1, 1947 a XY djffymw ASW @ro Orem?""39 @Mm-W; f

Patented Dec. 14, 1948 MICROMETER BOIGEl GAUGE' Harold Eorsmark,Chicago,y Ill., assigner v@to Stiger Precision Products, Inc., Chicago,,Il-1.,.a ,corporation-prof .-Illi-njois ApplieatonMarch 1, 194,7,SelNo. '7313'731116- (CL. .S3-4,78.)

Z-Glaims. l,

My `invention relates, .generali-y, `.to l.gage constructions andithas'y :particular rel-ation Ito the construction of gages for measuringaccurately the diameter nof hores, such as bores in metal blocks andithe flike.

In measuring the diameter cfa boreiina metal Ablock. atnasubstafntialdepth, it isconventional to Iusefza; telescoping ygage to obtain alength which can be measured separately' by an loutside micrometer..This' procedure. is,l objectionable .for several .freasons.. .It isnecessary to provide some clearance :to `removal rof the telescoping`gage from fthe bore. .tol diameter `.being measured is .reduced byabout A1602 inch aiml allowance' must be. made for ,suohlreriuction' indetermining theaetual bore diameter; y'Twooperatior'is are requiredtormeas- Aure the bore diameter when vthis .procedure is followed. This'increases the time required vfor "obtaining .the measurement. Twodifferent instruments are required .for ,performing such opera/tions.

Aceordinglm among `the objects of my invention are.: To overcome-theforegoing and other objections in. the measurement .of the diameter ofbores; to `provide a. direct reading of the `loore .diameter .in asingle operation; to provide vindicia Von Ythe `barrel and thimble ofthe gage that `are relatively far apartso .as to facilitate reading of.the same; .to move a pair of balls vapart to contact the bore .surfacefor adjusting the gage tomake the vbore measurement; to prevent the'ballsi'from escaping while permitting free movement thereof' within therange 'of the gage withv,out `peening or otherwise deforming7 the lheadthat holds Athe balls; and to `permit operation of the gage by one hand.

Other objects of my invention will, vin part, VVbe obvious and in partappear hereinafter.

My invention isv disclosed' in the embodiments thereof shown in theaccompanying drawing, 'and it comprises the features lof construction,combination of elements, and' arrangement of yparts which will beexempliedin the .construc- Ition hereinafter set forth, and the scope ofthe application of which Kw-ill be indicated in the appended claims' Fora more ycou-iplete understanding of the 'naturefand scope of myinvention, reference may be had 'to the following detailed description,taken `togetiier with the accompanying ydrawing fin which;

Figure l 'is 1a. IView :showing my improved. bore gagefheld' tuft'hehand: of an operator. fand inserted im aboreformeasuringthe'diameter'thereofl;

The length. corresponding 2 Figures' 2,. .3-v and-'4 :detail sectional..takenr :along 'the lines .Z-.-.2,. :and ii-i4' of Figure. l;

Figures .5 and: s6,- are: detail sectional uViews,.tadren 'Eigu-.re 'Z.is a,..detaiil,fseetional view-` .of .a modified end :portion of myimprovedabone gage v-tztkxen iat right angles "to `:the section ish-own.Vin @ingiere- Referring. now patiticui'arly to'fFiJgur-e :l .of thedrawing, vit will :be :notedithat' 'the arefunzen-ee.ictxara acter 8desiginates, .generaily, .a boreI .gage :in `which my invention "is`embodied. AThe. gage. f8 shown inoperative position 'for Aine'assurin'gthe diameter yof afboreu Svinia block for :shell im. :Forillustrativefpurposes, it maybe-:assumed thatftn'e nominal diameter .ofther bore :9:- fis oneahalr inch and' thatl the: gage. & sis intendedtoimeasure-,diameters: 4ran-ging:above and? beiowwoneehailf by .050 incho1'. thereabout'.v It be understood vdiiferent =gages vare, providedttor luse in measuring the `diameters of larger :or smallerv bores. It'is with this understanding that `wtrious `.dii-'melf/:sions arereferred to herein as' ybeing applicable-.to lthe .construction of a:gage for measuring fbore l.dilameters which` nominally 4are` close 'toone-=halff inch.. 'For measuring other diameters the Igage kdimensionslin some. or all respects honor-re- .spondingly different.

As shown inthe drawing, thefgagei includes a barrel' .ortubular bodylilv which may have-'an external diameter oth-5% It vmay be termed ofsuitable-.steel .rods-took. A thimble or terruile 122 .of similarmaterial isv thrleadedon the barrel v'or tubular fbody 'I` I' and iii-isknurled, yas indicated aty 1.3, to facilitate its being gripped 'fbyfthe dore- 4iingerfandthumbfeti/an operator. the endof the thimble orferrule 1| 2 there is :provided an adjusting sleeve I4, the unction -ofwhich will] be described presently. .The adjusting sleeve F4 may be`secured '.tothe Sth-imble or Terr-die yi2' by means of a dogl pointsocket set vscrew iii. `The router end `of 'the adjusting sleeve I4maybefclosed by ay knfurled capY fI|6',Which,. will appear hereinafter,is threaded tinto) the-"same The barrel or tubular bodyv4 HIisz-providedfwih :indieia .orcQbrating'marKSFi 1:' withl which indiciaor -calibrating .marks :lili on` thef'thimbl'e SI 2' coopcrate.v Thepitch of: .the threaded. engagement `between the :barrer` or tubular:hodyf tali Aanun-the .thimbie or ennuie gl Zis :so ehosenthat'theindicia Is'lv and 1:8' canne spaced; rela/timely aparts-so to facilitateinspection and'. reading: thereof. The manner which this be amcomoiishedwillilfeisetforth:presently i 'llnreftorita'ot .engagement withthe.inner suriwce for permitting free longitudinal movement thereof. Theexternal diameter of the head 23 is equal to the external diameter ofthe barrel or tubular body so that, in effect, it constitutes alongitudinal extension thereof. The head 23 preferably is formed ofhardened steel which cannot be deformed by peening or otherwise forholding the balls 2l therein without disturbing the accuracy of the head23. It is within the scope'of my*A in..`

vention to employ pins with hemispherical ends instead of the balls 2|for measuring the diameter of bores that are substantially larger thanthe .bore 9, for example, for the measurement of bores having a nominaldiameter of two inches or more.

Surrounding the barrel or tubular body is a clamp ring 24 to which aring 25 may beadjustably secured. The ring 25 has an integrally formedshank 26 that, as shown in Figure 4, may be positioned between theoutwardly extending ends of the ring 24 and securely clampedin place bya clamp screwZl, By loosening the screw 2l, it is possible to adjust theposition of the ring 25 to suit the convenience of the operator. Thepro- Vision of the ring 25 permits the operator to hold the gage 8 withone hand and at the same time to adjust the thimble or ferrule l2 by theforelinger and thumb as illustrated in Figure l.

The clamp ring 24 has another function.- -It serves as a stop for theforward movement of the thimble or ferrule |2 and thus prevents theballs 2| from being forced out of the head23.V

In Figure 2, the internal details of construction of the gage 8 areshown more clearly. It will be noted that the head 23 has an integrallyformed reduced diameter hollow portion 3| thatfhas external threads 32for cooperationv with internal threads 33 of the barrel or tubular bodySince the diameter of the transverse cylindrical opening 22 in the head23 is slightly greater than the diameter of the balls 2|, it isnecessary to provide means for preventing the balls 2| from escaping. Atthe same time the means which is provided for performing this functionmust `not interfere with the free movement of the balls 2| in thecalipering of a bore. For this purpose the outer end of the barrel ortubular body il is undercut as indicated at 34, so as to provide a lip35 which extends a slight distance intothe ltransverse cylindricalopening 22 at each end,

and thus into the paths of outward movement of the balls 2|. This lip 35is sufficient to prevent loss Vof the balls 2| from thetransversecylindrical -opening 22. At the same time it does not interfere withtheir free movement within the-range of the gage. Moreover, there is nochange in the external diameter of the barrel or tubular body or of thehead 23.

The balls 2| are movedapart by a rod 36 that has a conical end 3l forengaging the juxtaposed surfaces oi the balls2| as shown in Figure 2.Because of the wear incident to the movement of the balls 2|, itis'preferable that the' conical end or tip 3l be'hardened or that a:separate carbide tip be provided on the end of the rod 36. The end ofthe rod 36 adjacent the conical end or tip 3l extends through the`reduced hollow portion'y 3| `of the head 23. Thelinterme- `tion of therod 36.

diate portion of the rod 36 is threaded as indicated at 38. The thread38 is relatively fine. For example, there may be 56 threads to theinch.The ne thread 38 promotes the accuracy in the movement of the balls 2|and permits relatively ne adjustment of their positions. The barrel ortubular body l is internally threaded, as indicated at 39, for,vcooperating with the threaded section 38 of the' rod 36.'- The barrel ortubular body is provided with a threaded reduced extension 40 that isslotted, as indicated at 4|, which. is illustrated more clearly inFigure 5. Shims 42 of compressible material are provided in the slots 4|and an adjusting nut 43 is threaded on Ythe extension 40. It will beobserved that the extension 40 is conical in shape so that when theadjustingnut 43 is tightened thereon, the portions of the extension 4|)between the slots 4| will be moved inwardly slightly. The purpose ofthis construction is tov compensate for wear of the threads 38 and 39which results from repeated -use of the gage after it has been inoperation for sometime. f; .v

The barrelvor tubular body is provided with external threads 4d forcooperating with internal threads 45 onl the thimble4 or ferrule l2.lThese threads are relatively coarse for the reasonindicatedhereinbefore.. For example, there may be ten threads double per inch.

Because of the difference in pitch' between the threads on the rod 38and the threads or",V the thimble or ferrule l2, provision mustzbemadefor permitting relative longitudinal movement therebetween. This isaccomplished in accordance with my invention by'providing flat portions46 on opposite sides of the outeren'd of the rod 36. These sidesinteri-lt with a transverse slot 4l, Figure 6, in the adjusting sleevevI4. so that when the latter is turned, the rod 36 also is turned butlongitudinal relative movement therebetween is permitted. It will beobserved that the point of the set screw |5 projects into an annularslot i8 in the adjusting sleevell. The set screw I'5 serves to hold thesleeve I4 in fixed relation with vrespect to the thimble or ferrule |2.`Initially set screw4 l5 loose until the balls 2| engage the standardbore. Then the thimble or ferrulelZ is adjusted until the Zero mark ofthey indicia I8 registers with the point .500 mark'of the indicia l1.Thereupon the set screw I5 is operated to securely clamp the adjustingsleeve |4 to move with the thimble or ferrule |2.

' As shown in Figure 2,V the cap |6 has a longiytudinal axial aperture43 therein to receive the hat end 46 of the rod 36. The cap |6 hasexternal threads 56 that interfit with internal threads5| at the outerend of the adjusting sleeve i4.

When the forward end of the adjusting sleeve I4 engages the rear end ofthe extension 4|]- of the barrel or tubular body the former cannot berotated further to cause additional forwardrota- Thus, if. the clampring=24 is omitted or is improperly placed so that it.does not functionas a stop as described hereinbefore, the rod 36 cannot be movedforwardly to'such an extentl thatitfwll force the: Aballs 2l past Vthelip 35 and permit them to escape from the cylindrical opening 22 in thehead 23.

In Figure 7 of the drawing, a modified construction of the forward endportion of the gage is shown. An extension 52 of the barrel or tubularbody I I may be provided so that together they form the equivalent ofthe barrel or tubular body II previously described, The barrel II hasinternal threads 53 for cooperating with external threads '54 on theextension 52 to permit joining of these parts together.

One reason for the construction just described is to permit the use ofcertain of the parts making up the gage 8 for the various sizes thereof.The same barrel or tubular body II, thimble or ferrule I2, adjustingsleeve I4 and cap I6 can be used for a wide range of sizes of the gage.In general the parts that are individual to a particular gage size are:the head 23 or 23', the balls 2l, the rod 36 and the extension 52.

The head 23 shown in Figure 7 is different from the head 23 describedpreviously in that it has a bevel face 55 which intersects thecylindrical opening 22 rather than a flat radial face as is the case forthe head 23. 'Ihe extension 52 has a corresponding bevel face 56 whichengages the face 55 and a portion thereof, corresponding to the lip 35,projects into the ends of the cylindrical opening 22 and serves toprevent the balls 2I from escaping. This construction, of course, can beused for the head 23 and the barrel or tubular body I I shown in Figures1 and 2.

Since certain changes can be made in the foregoing construction anddifferent embodiments of the invention can be made without departingfrom the spirit and scope thereof, it is intended that all matter shownin the accompanying drawing, and described hereinbefore shall beinterpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A bore gage comprising, in combination, a cylindrical tubular bodyinternally threaded at one end and externally and internally threaded atthe other end, a cylindrical head having a diameter equal to that ofsaid body and a reduced hollow externally threaded portion for enteringsaid one end of said body whereby the head constitutes a cylindricalextension of said body, said head having a transverse cylindricalopening therein, a pair of balls having diameters slightly less thanthat of said cylindrical opening, movable apart therein to projectbeyond said head for engaging the surface of said bore, the end of saidbody adjacent said head being undercut to provide a circumferential lipabutting said head and intersecting said cylindrical opening therein toprevent said balls from escaping therefrom, a rod axially disposedwithin said body and hollow portion of said head and cone shaped at oneend for engaging said balls to move the same apart, said rod beingthreaded intermediate its ends for engagement with the internal threadsat the other end of said body and having the other end flattened on twoopposite sides and projecting from said body, an internally threadedthimble threaded on said other end of said body, an adjusting sleevesecured to the outer end of said thimble and having a slotted openingslightly greater in width than the distance between said flattened sidesof said rod for receiving and rotating the same on rotation of saidthimble while permitting relative longitudinal movement therebetween,and indicia on said body and sleeve to indicate the diameter of the borebeing gaged.

2. Adjusting means for a micrometer comprising, in combination, a barrelhaving internal and external threads, a rod threaded in said internalthreads and constituting a movable measuring element of the micrometer,one end of said rod having parallel sides and extending beyond one endof said barrel, a thirnble threaded on said external threads of saidbarrel, and an adjusting sleeve movable lwith said barrel and having aslotted opening slightly greater in width than the distance between saidparallel sides of said rod for receiving and rotating the same onrotation of said thinlble while permitting relative longitudinalmovement therebetween.

HAROLD R. FORSMARK.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number

